## Terms and Definitions

### Symbols, Descriptions and Units

Symbol | Meaning | Metric Units |
---|---|---|

C | Capacitance | farad |

C_{ij} | Elastic stiffness constant | newton/meter^{2} |

C_{0} | Shunt capacitance | farad |

C_{1} | Series capacitance | farad |

d_{ij} | Piezoelectric strain constants | coulomb/newton |

d_{33} | Piezoelectric strain constant | x 10^{-12} Meter/Volt |

d_{31} | Piezoelectric strain constant | x 10^{-12} Meter/Volt |

d_{15} | Piezoelectric strain constant | x 10^{-12} Meter/Volt |

E | Electric field | V/m |

f_{a} | Antiresonance frequency | cycles/second |

f_{r} | Resonance frequency | cycles/second |

f_{n} | Frequency of max. impedance | cycles/second |

f_{m} | Frequency of min. impedance | cycles/second |

f_{p} | Parallel resonance frequency | cycles/second |

f_{s} | Series resonance frequency | cycles/second |

g_{ij} | Piezoelectric voltage constants | meter^{2}/coulomb |

g_{33} | Piezoelectric voltage constant | X 10^{-3} voltmeter/newton |

g_{31} | Piezoelectric voltage constant | X 10^{-3} voltmeter/newton |

g_{15} | Piezoelectric voltage constant | X 10^{-3} voltmeter/newton |

h_{ij} | Piezoelectric pressure constants | newton/coulomb |

K_{ij} | Electromechanical coupling constant | |

k_{31} | Transverse coupling constant | |

k_{33} | Longitudinal coupling constant | |

k_{15} | Shear coupling constant | |

k_{t} | Thickness coupling constant | |

k_{p} | Planar coupling constant | |

K^{T} | Free relative dielectric constant | |

K^{S} | Clamped relative dielectric constant | |

P | Electric polarization | coulomb/meter^{2} |

Q_{M} | Mechanical quality factor | |

Q_{E} | Electrical quality factor | |

S_{ij} | Elastic compliance constant | meter^{2}/newton |

|Y| | Admittance | mho |

|Z| | Impedance | ohm |

### Terms and Definitions

#### Curie Point

The temperature at which the dielectric constant peaks and all polarization disappears.

#### Coupling Coefficient (k)

A dimensionless number related to the ratio of the energy stored in the mechanical and electrical portions of the material. The first subscript indicates the direction of the electric field and the second indicates the direction of the mechanical strain, expressed in percent.

#### Density

The ratio of mass to volume in the material, expressed in kg/m^{3}.

#### Dielectric Constant

The ratio of the permitivity of the material to the permitivity of free space. The value specified is for the "free" condition (i.e., unclamped and well below the mechanical resonance of the part).

#### Dissipation Factor

A measure of the dielectric losses in the material defined as the tangent of the loss angle or the ratio of parallel resistance to parallel reactance expressed in percent.

#### "d" Constant

The piezoelectric constant relating mechanical strain and applied electric field - defined as the ratio of strain to field. The first subscript indicates the direction of the field and the second the direction of the resulting strain, expressed in meters/volt.

#### Field

The ratio of voltage developed to the distance between the electrodes.

#### Frequency Constant

Defined as the resonant frequency (f_{r}) times the controlling dimension, expressed in KHz-m.

#### "g" Constant

The piezoelectric constant relating open circuit voltage and mechanical stress - defined as the ratio of voltage to stress. The first subscript indicates the direction of the generated voltage, and the second indicates the direction of the force, expressed in volt-meters/newton.

#### Mechanical Q (Q_{M})

The ratio of reactance to resistance in the equivalent electric series circuit representing the mechanical vibrating resonant system. The shape of the part affects the value.

#### Strain

The ratio of the change in length to the length.

#### Stress

The ratio of applied force to the cross sectional area.

#### Young's Modulus (Y)

The mechanial stiffness property of a piezoelectric ceramic material and is expressed as the ratio or stress to strain the material, while vibrating at its resonant frequency, expressed in newtons/meter^{2}.